The invention relates to an on-line or in-situ method of assessing wear and/or damage that has occurred to turbine parts. The invention also relates to a gas turbine comprising parts with smart coatings and collection and detection means to measure wear and erosion of gas turbine parts.
The current industry practice for determining wear and damage of gas turbine parts is schedule-based shutting down of a turbine and physically examining parts at predetermined intervals. However, this process is highly inefficient, time consuming, and costly due to turbine shut-down and maintenance. In response, general on-line or in-situ methods have been developed for detecting wear-out of outer surfaces of wear-susceptible parts.
For example, Blatchley and coworkers (C. C. Blatchley and R. J. Bricault Jr., in Tribological Mechanisms and Wear Problems in Materials, ASM International, Metals Park, Ohio, 1987, pp. 95-100 and C. C. Blatchley and P. G. Loges, in Advances in Steam Turbine Technology for Power Generation, ASME, New York, N.Y., 1990, Vol. 10, pp. 9-13) developed a xe2x80x9csurface layer activationxe2x80x9d technique to monitor wear and corrosion in steam turbines by detecting gamma-ray signals from radionuclides imbedded in trace amounts in surfaces of wearing parts. The nuclides served as surface markers, and were produced by controlled exposure to particles from Van de Graaff or cyclotron accelerators.
However, the above techniques can only be applied to steam turbines, which are closed systems, so that radioactive materials in the water stream will not be released to the environment. The technique cannot be applied to gas turbines because the exhaust is released into the air, and radioactive elements will be detrimental to the environment.
Other existing coating life estimation methods are typically based on average effects of stress and temperature profiles of all the parts. These methods are unable to focus on individual parts because they do not take into account the circumstances that the parts installed in a particular turbine actually encounter, such as foreign object damage, variation of operating conditions from site to site, and occasional overfiring of the turbine. All of these circumstances can drastically influence the true remaining life of the individual parts.
Thus, there exists a need for an on-line or in-situ assessment of coatings and wear of gas turbine parts, without turbine shut-down or disassembly. Accordingly, an online or in situ method for detecting wear and/or damage of gas turbine parts is desirable. Also, a gas turbine which can be efficiently, and reliably measured online or in situ for wear, is also particularly desirable.
There is provided, in accordance with one preferred embodiment of the invention, an on-line method of assessing wear and/or damage to gas turbine parts, comprising the steps of: (a) coating one or more gas turbine parts with a coating comprising a taggant; (b) collecting and concentrating particles of an exhaust stream which passed over a part coated in step (a) to provide a particulate containing fraction; and (c) analyzing the particulate containing fraction for the taggant, whereby the presence of a taggant indicates wear and/or damage to the gas turbine part.
There is also provided, in accordance with another preferred embodiment of the invention, a gas turbine, comprising: (a) one or more gas turbine parts coated with a coating comprising a taggant; (b) an exhaust collector in fluid communication with the gas turbine parts, whereby the collector samples a portion of an exhaust gas which passed over the coated gas turbine parts; (c) an exhaust particle separator connected to said particle collector, whereby the separator separates and concentrates particulate matter in the exhaust gas; and (d) an optional analyzer connected to the separator, wherein the elemental analyzer is capable of detecting the taggant.
There is also provided, in accordance with another preferred embodiment of the invention, a part for a gas turbine comprising: a) a turbine component substrate; and b) an environmentally resistant coating applied on the turbine component substrate. Preferably, the environmental coating or the coating/substrate interface comprises a taggant selected from the group consisting of Sr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Re, Ru, Pd, Pt and Au. Preferably, these elements are present exclusively as taggants so that their collection pinpoints where damage has occurred.
There is also provided, in accordance with another preferred embodiment of the invention, a part for a gas turbine comprising: a) a turbine component substrate; b) a bond coat applied on the turbine component substrate; and c) a thermal barrier coat (TBC) applied on the bond coat, wherein the TBC or a TBC interface comprises a taggant selected from the group consisting of Sr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and the bond coat or a bond coat interface comprises a taggant selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Re, Ru, Pd, Pt, and Au, and wherein the TBC or TBC interface taggant is different from the bond coat or bond coat interface taggant. There is also provided, in accordance with another preferred embodiment of the invention, a gas turbine, comprising: (a) one or more gas turbine parts provided with a coating comprising a taggant; (b) a collector means for sampling a portion of an exhaust gas which passed over the coated gas turbine parts; and (c) a separator means for separating particles from the exhaust gas.